The steels used for parts situated upstream from an exhaust system of a motor vehicle, the hot part of the system, must have both good resistance to oxidation and good creep resistance. Good formability is also necessary for manufacture of the manifold. The steels used for these hot parts are often either austenitic steels, which are relatively expensive and have poor oxidation resistance, although their formability is good, or bistabilized ferritic steels. The bistabilized ferritic steels have good oxidation resistance but are relatively difficult to form.